The present invention relates to a grinding wheel for the grinding of ophthalmic glass blanks, of the type comprising a disc-shaped core which carries a diamond-charged abrasive layer on its periphery.
Such a grinding wheel is intended for equipping a grinding machine, in particular an automatic one, which can be used for routing the blanks of spectacles or glasses.
To fit an ophthalmic glass in the circle or surround of a spectacle frame, a generally circular glass blank is taken as a starting point, and then this blank is routed to the contour of the frame circle. The blank routed in this manner is subsequently passed to a finishing station.
The routing of ophthalmic lenses is usually carried out on an automatic grinding machine. This machine possesses one or more abrasive grinding wheels which are driven in rotation at high speeds and serve as tools for cutting the edge of the spectacle glasses.
When the lenses to be ground are mineral glasses, the grinding wheel must comprise a diamond-charged abrasive layer, and this abrasive layer is carried out by a disc-shaped rigid metal core.
Automatic grinding machines generally comprise a wheel-holding shaft provided with means for driving in rotation at high speeds, and means for supporting a glass blank, which is designed to cause the blank to rotate at a slow rotational speed along a supporting axis parallel to the wheel-holding shaft. The machine also includes means for varying the distance between the two axes as a function of angular position of the blank about the supporting axis.
During the use of the grinding wheel, it has been discovered that a middle part of the length of the grinding wheel undergoes more rapid wear. It is therefore necessary to change the grinding wheel well before the entire abrasive layer is worn. This is particularly troublesome in view of the high costs of diamond-charged products.